A little better than stock? Or not?

Cleatus12r once said:

And CSIPSD once said:

Riffraff Diesel Performance says:

"Injector Description:

AA - '94-'97 Non-California trucks. They are all 90cc injectors and are single shots.
AB - '97 California, and all Early '99 trucks. Split Shot injectors that flow 130cc of fuel.
AC - Came in high torque version of the T444E and didn't come in any Powerstrokes. They have the same internals as the AB injectors with the exception of the single shot plunger and barrel and are 160cc.
AD - These are found in all late '99-'03 Powerstrokes and T444Es, and are a Split Shot Injector
AE - Long lead AD injector that was used to cure a ‘cackle’ issue."

[Unfortunately, Riffraff does not list the cc flow rate of the Ford stock AD/AE stock nozzles. If Riffraff or someone else who knows would chime in here with that info, it would be appreciated.]

IIRC, Shake-N-Bake selected stock AD split shots, while Franko72 (and I believe SkySkiJason) selected stock-like AC single shot injectors (with a little larger nozzle for a little more fuel flow?).

So, the question posed on this thread is:

Looking for stock like drivability, a small HP/performance gain, with the same or better engine longevity, what are the benefits/detriments/risks of installing all new Alliant AC Code Stock IH Injectors in our Ford 7.3L Power Strokes?

In other words, if the 7.3L was originally designed for single shots, is its drivability, performance or longevity repressed by the split shots and can we achieve better or the same drivability/performance/longevity by installing new Alliant AC Code Stock IH Injectors with the International Harvester oem PCM or an aftermarket tune approximating it?

Or are the Ford 7.3L PCM, IDM, and other engine sensors and systems so redesigned by Ford to work with the stock AD split shots that it would be a never-ending PITA to attain stock-like drivability, a small HP/performance gain, the same or better engine longevity such that it would be just better to stay with stock AD Code injectors?

 

AC codes were OEM new on some IH trucks and I'd expect OEM new performance. Only mod you'll need is tunes to run singles. Same IDM etc without mods. And more than small hp gains at the expense of a little more noise. The purpose of split shots is to reduce noise.

 

I have seen some literature that says AB codes are 120cc and other documents that give 130cc as the spec so there may be a couple of versions produced.

In my opinion....with proper tuning, AC injectors with stock nozzles will idle and drive just as well as stock AD units. The only possible side effect might be a slightly louder engine that may also smoke a bit more. One would have to be very familiar with the 7.3 engine to recognize the difference.

From what I have read, split shots were a sort of band aid that was intended to quiet down the engine and help reduce the amount of smoke at idle or very light throttle. Back when the Super Duty was released, the buying public had a perception that diesel engines were noisy, stinky and filthy. Split shots were used to help change that notion. The trade off is that a little bit of fuel is wasted in the process of each injection event. Splits also require a little bit more oil volume and pressure to operate. I believe AD codes are 140cc. That must have been enough of an increase over AB sticks to warrant a higher volume HPOP (15 degree vs 17 degree).

Interestingly enough, the jump from AD to AC is about the same as AB to AD in terms of cc/1000 strokes yet the AC injectors do not require a higher volume HPOP. This is because the single shots are more efficient with oil when compared to splits, so a 17 degree pump is just fine in all but extreme cases. I am told that tuning for AC injectors becomes more complex when modified pumps, turbos and nozzles are factored into the equation.

I really wanted to go with AC injectors for my last build but it would have cost me about $1000 more, ($500 for plungers and barrels and $500 for new custom tunes). If I didn't already have a chip, then I would have prefered to go with the AC sticks and stock nozzles. In my opinion, things are always a compromise so while 100% nozzles will yield more peak HP...stock nozzles may have a broader torque curve which may be better for towing. I have seen a few dyno graphs that sorta gives me indications that may be the case. Plus, stock nozzles should be easier to tune as well.

In my opinion, if someone with an otherwise stock engine is getting custom tunes and new injectors then it is hard to go wrong with AC sticks and stock nozzles.

 

If I had to do the single shot AC codes all over, I'd get AC's with 100% nozzles.

I love the AC's in my old F250.

Stewart

 

Me too! I wish I could change the nozzles right now - while engine is out... Donations anyone? Santa, did you get my letter??

The AC's in my dually run 100% 'as good as stock' with no adverse side effects whatsoever. In my '60 tow' tune there is zero smoke and it dyno'ed at 320hp with a 38R. I literally never even look at my EGT gauge anymore while towing at 24k lbs GCVW and I drive like I stole it!! Of course, there is always 370hp on tap should I feel the need to twist that little ****!!

 

i put new stock ac's in but along with a 38r , exhaust , 6637 , and a tuner . i love it in stock tune its the same but with more power and in 80e or 100 performance its a rocket!

 

I went with 100% nozzles because it was said EGTs could be lowered even more than the stock nozzles... but if one is not careful with tuning, you can unleash a little too much power. I am dealing with that last part now. ACs with stock nozzles will not likely disappoint... you will get a big bump in power, they can be tuned about as quiet as stock, and they will lower EGTs. ULSD took care of the stink that was notorious with diesels... but you really need fuel additive and the fuel/FRx mods to aid with the quiet operation (ACs or ADs).

 

Great question Tim, thanks. Subscribing for sure.

 

Hey guys, I don't understand "100%" nozzles compared to "stock" nozzles. Assuming that "stock" nozzles are the ones which normally come with new AC Code Stock IH Injectors, they have a particular (but not specified in Riffraff's chart) cc fuel flow, right? But what is a "100%" nozzle? Assuming that it has larger fuel flow, what is its cc specification? And what is the whole % thing based on?

Also, although it hasn't been brought up yet, I have totally given up on "stages" when trying to understand injectors. A manufacturer's "stage" seems to be a shorthand way of describing the quality and amount of parts used in a remanufactured injector which is not consistent across manufacturers. Since this thread is only directed to new injectors, isn't the whole "stage" discussion irrelevant to this discussion?

Shake-N-Bake: I realize that I am kinda hijacking my own thread here, but another question. If AD Code split shot injectors are 140 cc and AA Code single shot injectors are 90 cc, but more efficient, then would we get more mpg with new AA Code stock single shot injectors? Has anyone done this? Also has anyone added a 130 cc nozzle to an AA Code injector or downsized to a 130 cc nozzle on an AC injector? Thinking mpg here.

Also, is it o.k. to put AC Code injectors in an engine with powdered metal cylinder rods (PMR's)?

 

AC codes are 160cc injectors. Stock split-shots can deliver ~130cc. This number is just the POTENTIAL of the injector, the actual fuel delivery is dictated by Pulse Width (PW). To a point, you can have much larger plunger/barrels = much more cc's - and still have a truck run like 'stock'.

I have driven a truck with 250/200's and unless you smash the loud pedal - you would NEVER KNOW!!!

The nozzles are often referred to as % over stock. A '30% over' nozzle allows that much more fuel to flow thru the nozzle. The advantage of bigger nozzles is being able to put the same amount of fuel in the combustion chamber in less time - shorter PW. A long PW can either inject 'early' and raise CP's (cylinder pressures) - aka advanced timing - or inject 'late' which raises EGT's and makes more smoke. By reducing the PW, to some extent you get a 'cleaner' burn with the same amount of fuel.

You are SPOT ON with the 'stages' observation. This is a ridiculous way to refer to injectors. Although, typically a Stage 1 injector is referring to 160cc AC codes - Stage 1.5 to Stage 2 could be anything from 175cc with stock nozzles or 160cc with 30% over nozzles up to 100% over nozzles.... Stage 3 are typically 'hybrids' with P&B's up to 400cc.

Yes AC Codes are FINE with PMR's - as long as ya have good tuning! Mine, with a 38R made 370HP in hottest tune. Well below the 400HP 'glass ceiling' of PMR's.

 

Simply put % oversize nozzles means that each of the 7 holes in the nozzle are that percentage larger in diameter over stock. 50% means each hole diameter is one and a half times larger than stock. 100% means each nozzle hole diameter is twice as large as stock.

 

Nozzles have nothing to do with the volume rating (cc) of the injector. The internal parts of the injector body determine the maximum cc capacity that can be delivered while the nozzle determines how fast that fuel can be injected. Smaller nozzle holes means it will take more time to deliver the same amount of fuel, this is why many folks like larger nozzle openings so they can obtain more performance.

Another thing to remember is that cc size is only relevant when at higher pulse width and ICP values. There is no reason to use a 90cc injector for fuel economy because a 200 cc injector will be just as economical provided the driver is gentle with the go pedal. By varying the pulse width and IC pressure, the fuel charge can be controlled pretty well. A larger injector has more 'head room' compared to a smaller injector. It's generally agreed that a stock AD injector is the limiting component in these engines in regards to mechanical ability to make power. Adding 160cc injectors is a more reasonable size to install (and about the limit) if the stock turbo and HPOP etc is retained. If you want more power than a 160cc can provide then you are probably going to need to increase your budget for more stuff to compliment whatever size injectors you choose to run.

Tuning is super critical because the 7.3 has an Open Loop injection control system. This means the PCM has no way of calculating how much fuel was actually injected so it has to be correct the first time. Gasoline engines have sensors in the exhaust system that can measure air/fuel ratios and adjust the computers calculations via 'fuel trim' values. Some have what's called Short Term fuel trim and Long Term fuel trim. Some have fuel trim by bank (v engines) and others have fuel trim by cylinder (EcoBoost). The new 6.7 has 4 EGT sensors in the exhaust system and I am pretty certain they are using at least one of those sensors to come up with a fuel trim value of their own.

 

Shake-N-Bake: I have read quite alot on FTE because I don't expect to be spoon fed through my threads ...

But I am blown away by your last post. It has truly exposed my ignorance. Can you suggest a good read on how the 7.3L fuel control system and how injectors work? If not, will you and others please kindly continue my and our FTE brethrens' education?

Each sentence in your last post increased my knowledge and exposed how little I know about our engines.

 

I hate to break this to you Tim, but there a lot of us hanging on those words!
I have over thirty years being a mechanic (or tech), with GM and then Honda. Mostly at the dealership level. I never had any idea how much there was to know with these trucks. Heck I was confused trying to figure where the injectors were, then to find out they "run" off of very hi oil pressure. Unfortunately, the box is open, so just got to keep learning now, and of course spending a lot of "buckzooka" bucks.

 

SSJ: Your post when read with Shake-N-Bake's are helping. Sometimes I need to hear the same thing said more than one way to start to understand.

Is the 250 a cc rating? And the 200 a nozzle % over stock rating in the foregoing quote?